OF ARTS AND SCIENCES. 77 



Five to One Series. — Salts of this series were discovered at an 

 early period in the history of the subject by Zenker.* The ammonium 

 salt was analyzed by Zenker f and Werncke.t and recently by Ram- 

 melsberg.§ Debrny obtained the same salt, but has published no 

 analyses. Ramraelsherg also obtained the corresponding potassium 

 salt, as well as an acid salt of the same series. The alkaline salts are 

 colorless, and separate in well-defined crystals, which are usually easily 

 soluble in water. The acid of the series, as Debray has stated, can- 

 not be obtained by the decomposition of its salts, being resolved by 

 acids into free phosphoric acid and salts of the 24-atom series. The 

 decomposition may probably be expressed by the equation 



24 (5 M0O3 . rp^ . 3 11,0) = 



5 (24 Mobg . P,0, . 3 H,0) + 19 {V.f>, . 3 H,0). 



All the neutral salts are tribasic (old style) or more correctly hexa- 

 tomic, but well-defined acid salts exist in which the ratio of the molyb- 

 dic oxide to the fixed base is as 10 : 5. Such salts have been obtained 

 by Rammelsberg and by myself. The salts of the higher series are de- 

 composed by alkalies, as stated by Debray, salts of the 5-atom series 

 and alkaline molybdates being formed. Conversely, when a mineral 

 acid is added to a solution of an alkaline salt of the 5-atom series, a 

 salt of a higher series is formed, frequently as a yellow crystalline 

 precipitate. The neutral salts of this series hitherto described have 

 respectively the formulas 



5 M0O3 . Vp, . 3 K.,0 + 7 aq. 



5 M0O3 . PA • 3 (NHJ.P 4- 7 aq. 



5 M0O3 . P2O5 . 3 Na^O + 14 aq. 



5 M0O3 . P0O5 . 3 Ag,0 4- 7 aq. 



5 : 3 Phospho-mohjhdate of Ammonium. — This beautiful salt ap- 

 pears, as already stated, to have been first obtained by Zenker. It 

 is readily obtained by dissolving together five molecules of ammonic 

 molybdate and two of ammonic phosphate, and evaporating the solu- 

 lution, when beautiful prismatic crystals, with a glassy lustre, separate. 

 These may easily be purified by recrystallization. The salt is readily 

 soluble in hot, less easily in cold water. The solution has an acid 

 reaction, Zenker's analyses, as well as those of Werncke, agree 

 closely with the formula 



5 M0O3 . PPs • 3 (NIl4),0 -f 7 aq, 



* Journal fiir prakt. Chemie, Iviii. 256. t Loc. cit. 



X Zeitschrift fiir Analyt. Chemie, xiv. 12. § Loc. cit. 



